This year’s London mayoral race recalls the epic 1993 New York City rematch between David Dinkins and Rudy Giuliani, which Giuliani barely won despite Dinkins’ abysmal record.

On May 3, voters will choose between a cantankerous but principled conservative leader and an embarrassing leftist hack who hopes to piece together a winning coalition by sucking up to the seething underclass and the champagne socialists. London being even more left-wing than New York, it could go either way.

The city, divided into a warren of local governments called councils, only began metropolis-wide mayoral elections in 2000, after years of Giuliani-admiring newspaper columns asking why London couldn’t have a mayor like New York.

The 2000 and 2004 winner was the longtime Socialist “Red” Ken Livingstone, now the Labor Party candidate. In 2008, though, he lost to Boris Johnson. They’re squaring off again this year.

The boyish Boris, as he is universally known, is an admitted serial adulterer who has been the subject of at least three biographies. He cuts quite a figure with his ragged mop of white-blond hair and his Giuliani-like haranguing omnipresence.

Last week, he repeatedly shouted “you’re a f—ing liar” at Livingstone in a crowded elevator. Then he disclosed that he’d earned more than $750,000 last year, mostly as a freelance journalist.

Naturally, his poll numbers went up. He’d been down by two points to Livingstone — even after the latter’s comment, at a Hamas-linked London mosque, that he’d make the capital “a beacon that demonstrates the words of the prophet Mohammed.”

Now, after reports of the elevator face-off, Johnson is up six in the latest poll.

The inspiration for the Giuliani-esque “f—ing liar” remark was that Livingstone was, in fact, lying. He’d accused Johnson of funneling his earnings through a shell corporation to avoid paying high personal-income-tax rates. Boris had done no such thing.

Meanwhile, Livingstone had put his writing and speaking earnings through a dummy company (sole shareholders: he and his wife) to avoid the higher income-tax rates. (Bonus: Some Livingstone income came from hosting programs on Iranian state TV.)

The London mayor doesn’t have nearly the authority of New York’s (although he does oversee the transit system and has a say over the police). But the job brings high visibility, especially thanks to this summer’s Olympics. Many think Johnson’s charisma makes him the perfect man to step up and lead the Conservative Party in the event of the failure of the frail coalition government led by smaller-than-life Prime Minister David Cameron.

The moderate Cameron is often accused of being at best a lackluster defender of Conservative values. And he has fresh cause to be wary of his frenemy Boris: A Times of London-convened focus group of Tory-leaning suburban voters showed that it’s Boris, and very much not Cameron, who connects as a man of principle.

All seven voters in the group voted for Boris in 2008, but only one voted for Cameron two years later. Johnson is “mad as a hatter, but he makes me giggle,” said a woman. Added a man, “We need a strong leader, another Margaret Thatcher. At least she had the courage of her convictions. She’s like Boris Johnson, but in a different way. In a dress.”